CSS Variables Are A Sometimes Food

This article makes the important point that CSS custom properties - a.k.a. variables - are not a complete and ideal replacement for variables in preprocessors like Sass: they have different but overlapping use-cases, and custom properties are far better if used when cascading or changing the values in the browser are needed, while preprocessor variables are more performant for the browser when they perform the same role as custom properties, i.e. not repeating oneself. There’s also the issue of browser support for custom properties, but that’s another story.